Adhesive tape for jacketing elongate material such as especially cable looms and jacketing method

ABSTRACT

An adhesive tape, especially for wrapping cables, consisting of a preferably textile carrier and of a pressure-sensitive adhesive which is applied on at least one side of the carrier and is in the form of a dried polymer dispersion, the polymer being synthesized from:
         e) 90% to 99% by weight of n-butyl acrylate and/or 2-ethylhexyl acrylate   f) 0% to 10% by weight of an ethylenically unsaturated monomer having an acid or acid-anhydride function   g) 10% to 1% by weight of one or more ethylenically unsaturated monofunctional monomers different from (a) and (b)   h) 0% to 1% by weight of a difunctional or polyfunctional monomer   and the pressure-sensitive adhesive comprising between 15 and 100 parts by weight of a tackifier (based on the mass of the dried polymer dispersion).

The invention relates to an adhesive tape for jacketing elongatematerial such as more particularly cable looms in motor vehicles, and tomethods for jacketing.

Adhesive tapes have long been used in industry for producing cableharnesses. In this application the adhesive tapes serve for the bundlingof a multiplicity of electrical leads before installation or whenalready mounted, in order to reduce the space taken up by the bundle ofleads, by means of bandaging, and also, in addition, to obtainprotective functions.

The testing and classifying of adhesive tapes for cable jacketing takesplace in the motor vehicle industry in accordance with extensive bodiesof standards such as, for example, LV 312-1 “Protection systems for wireharnesses in motor vehicles, adhesive tapes; test guideline” (October2009), as a joint standard of the companies Daimler, Audi, BMW andVolkswagen, or the Ford specification ES-XU5T-1A303-aa (revised versionSeptember 2009) “Harness Tape Performance Specification”. In the textbelow, these standards are referred to in abbreviated form as LV 312 andFord specification, respectively.

The sound-damping effect, the abrasion resistance and the temperaturestability of an adhesive tape are determined on the basis of definedtest systems and test methods, as described comprehensively in LV 312.

Cable wrapping tapes with film and textile carriers are widespread,being generally coated on one side with various pressure-sensitiveadhesives (PSAs).

Cable wrapping tapes are required to meet three principal requirements.

-   -   a. Ease of unwind:        -   The product dispensed in roll form must be easily unwindable            for simple processing.    -   b. Flagging resistance:        -   Flagging—in the case of an adhesive tape wound around an            element—means the tendency of one end of the adhesive tape            to stick up. The cause is the combination of the adhesive's            holding power, the stiffness of the carrier and the diameter            of the cable loom.        -   In use, ends of adhesive tapes must not automatically            detach.    -   c. Cable compatibility:        -   The cable insulation must not become brittle as a result of            the influence of the adhesive tape in combination with            elevated temperature over a prolonged time period. A            distinction is made here, in accordance with LV 312, between            four temperature classes T1 to T4, corresponding to 80° C.            (also called temperature class A), 105° C. (also called            temperature class B(105)), 125° C. (also called temperature            class C) and 150° C. (also called temperature class D),            which the wrapped cables are required to withstand without            embrittlement for more than 3000 hours. It is obvious that            temperature classes T3 and T4 impose more stringent            requirements on the adhesive tape than the lower classes, T1            and T2. The T1 to T4 classification is decided not only by            the cable insulation material but also by the PSA and type            of carrier.

Cable wrapping tapes with PSAs based on natural rubber usually exhibitgood flagging resistance, but have an unwind force which increases overthe storage time, and especially at increasing temperatures. Moreover,they meet only the lower temperature classes for cable compatibility.

Similar characteristics are exhibited by adhesive tapes based onsynthetic rubbers (styrene block copolymers) such as SBS/SIS. Even thehydrogenated products are restricted in temperature class.

Furthermore, cable wrapping tapes with PSAs based on UV-crosslinkablepolyacrylic esters are encountered. These tapes meet the hightemperature classes, but tend towards flagging.

In connection with adhesive tapes for cable jacketing, there are threeknown patent literature citations that mention acrylates in the form ofpolymer dispersions:

EP 1 132 927 B1 embraces the use of acrylate compositions in bandagingtapes for cables, with the boundary condition of cable compatibilitythat is valid in the present case as well. There is express mention ofan acrylate compound which can be coated in the form of an aqueoussystem. The description mentions that the term “compounds” refers toready-to-process mixtures of polymers with the corresponding additives.There is, however, an absence of any specific indication that the term“additives” also includes resins.

On the contrary, it is in fact mentioned that the temperature stabilityof the adhesive tape is achieved specifically by factors including theabsence of resins.

According to EP 0 994 169 B1 it is frequently necessary to crosslink inorder to achieve sufficient cohesion (here in the sense of chemicalresistance). This in turn leads in general to a reduction in bondstrength and tack. The solution lies in a method for producing adhesivetapes by radiation crosslinking, producing effective cohesion whileretaining a high bond strength. The adhesives may also be resin-blendedacrylates from dispersion; there are no restrictions on the copolymercomposition.

DE 44 19 169 A1 describes a flame-retarded tape for cable jacketing, inwhich both the carrier and the adhesive comprise flame retardants. InExample 1, explicitly, an adhesive is mixed from raw materialscomprising Primal PS 83 D, a dispersion acrylate, Snowtack SE 380 A, adispersion resin, and flame retardant.

It is an object of the present invention to provide an adhesive tapewhich in spite of easy unwind has good flagging resistance and at thesame time exhibits cable compatibility across all designated temperatureclasses, and which allows the particularly simple, inexpensive and rapidjacketing of elongate material such as cable looms in motor vehicles.

This object is achieved by an adhesive tape as specified in the mainclaim. The dependent claims provide advantageous developments of theadhesive tape and methods for employing the adhesive tape.

The invention accordingly provides an adhesive tape, especially forwrapping cables, consisting of a preferably textile carrier and apressure-sensitive adhesive which is applied on at least one side of thecarrier and is in the form of a dried polymer dispersion, the polymerbeing synthesized from:

-   a) 90% to 99% by weight of n-butyl acrylate and/or 2-ethylhexyl    acrylate-   b) 0% to 10% by weight of an ethylenically unsaturated monomer    having an acid or acid-anhydride function-   c) 10% to 1% by weight of one or more ethylenically unsaturated    monofunctional monomers different from (a) and (b)-   d) 0% to 1% by weight of a difunctional or polyfunctional monomer    and the pressure-sensitive adhesive comprising between 15 and 100    parts by weight of a tackifier (based on the mass of the dried    polymer dispersion).

The adhesive is a pressure-sensitive adhesive (PSA), in other words anadhesive which even under relatively weak applied pressure allowsdurable bonding to virtually all substrates and which after use can bedetached from the substrate again substantially without residue. A PSAhas a permanently pressure-sensitive adhesive effect at roomtemperature, in other words possessing a sufficiently low viscosity anda high tack, and so the surface of the bonding substrate in question iswetted even with low applied pressure. The bondability of the adhesivederives from its adhesive properties, and the redetachability from itscohesive properties.

Acrylonitrile and/or methacrylonitrile preferably form the monomer (c)or at least part of the monomers (c), more preferably acrylonitrile.

2-Ethylhexyl acrylate preferably forms monomer (a).

According to another preferred embodiment, the monomer (a) consists of2-ethylhexyl acrylate and at the same time the monomer (c) or at leastpart of the monomers (c) consists of acrylonitrile and/ormethacrylonitrile, preferably of acrylonitrile.

One particularly preferred embodiment of the invention, therefore,comprises a mixture of 2-ethylhexyl acrylate as monomer (a) andacrylonitrile as monomer (c).

Contemplated advantageously as monomers (b) are, for example, acrylicacid, methacrylic acid, itaconic acid, maleic acid, fumaric acid and/ormaleic anhydride.

Preference is given to acrylic acid or methacrylic acid, optionally tothe mixture of both.

Monomers (c) include alkyl (meth)acrylates, preferably C₁ to C₂₀alkyl(meth)acrylates with the exception of the monomers forming (a),aromatic vinyl monomers such as styrene, a-methylstyrene andvinyltoluene, C₁ to C₁₀ hydroxyalkyl(meth)acrylates such as, moreparticularly, hydroxyethyl or hydroxypropyl(meth)acrylate, vinyl estersof carboxylic acids containing up to 20 carbon atoms, such as vinylacetate or vinyl laurate, vinyl ethers of alcohols containing up to 10carbon atoms, such as vinyl methyl ether or vinyl isobutyl ether, vinylhalides such as vinyl chloride or vinylidene dichloride, acid amidessuch as arylamide or methacrylamide, and unsaturated hydrocarbons having2 to 8 carbon atoms such as ethylene, propene, butadiene, isoprene,1-hexene or 1-octene.

Particularly preferred in accordance with the invention isacrylonitrile.

Examples of polyfunctional ethylenically unsaturated monomers (d) aredivinylbenzene, alkyl diacrylates such as 1,2-ethylene glycoldiacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate,1,8-octanediol diacrylate or 1,12-dodecanediol diacrylate, triacrylatessuch as trimethylolpropane triacrylate and tetraacrylates such aspentaerythritol tetraacrylate.

The polymer dispersion is prepared by the process of the emulsionpolymerization of the stated components. Descriptions of this processare given for example in “Emulsion Polymerization and Emulsion Polymers”by Peter A. Lovell and Mohamed S. El-Aasser—Wiley-VCH 1997—ISBN0-471-96746-7 or in EP 1 378 527 B1.

In order to obtain pressure-sensitive adhesive properties, the adhesiveat the processing temperature must be situated above its glasstransition temperature, in order to have viscoelastic properties. Sincecable loom wrapping takes place at normal ambient temperture(approximately between 15° C. to 25° C.), the glass transitiontemperture of the PSA formulation (polymer/tackifier mixture) ispreferably below +15° C. (determined by DSC (Differential ScanningCalorimetry) in accordance with DIN 53 765 with a heating rate of 10K/min).

The glass transition temperature of the acrylate copolymers can beestimated in accordance with the equation of Fox from the glasstransition temperatures of the homopolymers and their relativeproportions (cf. T. G. Fox, Bull. Am. Phys. Soc. 1 (1956) 123). Thetackifiers raise the glass transition temperature automatically,depending on amount added, compatibility and softening temperature, byaround 5 to 40 K. Consequently, only acrylate copolymers having a glasstransition temperature of 0° C. at most are suitable.

Preference is given additionally to polymers which in addition to thecomonomer composition of the invention have a bond strength to steel inaccordance with ASTM D3330 of at least 1.0 N/cm (for an adhesivecoatweight of 30 g/m² on a 23 μm polyester film carrier).

In the wrapping of a cable loom, the adhesive tape is bonded with fromno overlap at all to complete overlap around the cable, the radius ofwhich is generally small, meaning that the adhesive tape is very sharplycurved. At the end of a wrapped section, the tape is typically wrappedprimarily onto its own reverse face, so that the degree of overlap isvirtually complete, similar to the customary presentation form of anadhesive tape roll, where the adhesive is likewise bonded to its ownreverse face. In the event of flagging, static forces are acting, suchas, for example, through the flexural stiffness of the carrier and thewrapping tension, and may result in the open ends of adhesive tapestanding up undesirably, similar to the start of automatic unwinding.The flagging resistance, then, is the capacity of the adhesive to resistthis static force.

The polymer dispersion alone does not meet the requirements imposed onan adhesive tape for wrapping cables. In particular, the requiredflagging resistance is insufficient.

The use of tackifiers for the purpose of raising the bond strengths ofPSAs is known in principle. For the skilled person it is thereforeobvious to improve the flagging resistance by using tackifiers.Precisely this effect is observed if the adhesive is admixed typicallywith 15 to 100 parts by weight of tackifiers (based on the solids),usually 20 to 80 parts by weight, more preferably 30 to 50 parts byweight.

Surprisingly and unforeseeably for the skilled person, the use oftackifier resins in the case of the adhesive tape of the invention doesnot lead at the same time to difficult unwind, despite the fact that acommon factor of the two requirements is that the PSA has contact withits own reverse face.

Suitability as tackifiers, also referred to as tackifier resins, ispossessed in principle by all known classes of compound. Tackifiers are,for example, hydrocarbon resins (for example polymers based onunsaturated C₅ or C₉ monomers), terpene phenolic resins, polyterpeneresins based on raw materials such as, for example, α- or β-pinene,aromatic resins such as coumarone-indene resins or resins based onstyrene or α-methylstyrene such as rosin and its derivatives, forexample disproportionated, dimerized or esterified rosin, for examplereaction products with glycol, glycerol or pentaerythritol, to name buta few. Preferred resins are those without readily oxidizable doublebonds, such as terepene phenolic resins, aromatic resins, and morepreferably resins produced by hydrogenation, such as hydrogenatedaromatic resins, hydrogenated polycyclopentadiene resins, hydrogenatedrosin derivatives or hydrogenated polyterpene resins, for example.

Preferred resins are those based on terpene phenols and rosin esters.Likewise preferred are tackifier resins having a softening point of morethan 80° C. in accordance with ASTM E28-99 (2009). Particularlypreferred resins are those based on terpene phenols and/or rosin estershaving a softening point of more than 90° C. in accordance with ASTME28-99 (2009). The resins are usefully employed in dispersion form. Inthat way they can easily be mixed in finely divided form with thepolymer dispersion.

One particularly preferred embodiment of the invention, then, embraces amixture of 2-ethylhexyl acrylate as monomer (a) and also acrylonitrileas monomer (c) and terpene phenols and/or rosin esters having asoftening point of more than 90° C. in accordance with ASTM E28-99(2009).

To achieve further improvement in cable compatibility, the adhesiveformulation may optionally be blended with light stabilizers or primaryand/or secondary ageing inhibitors.

Ageing inhibitors used may be products based on sterically hinderedphenols, phosphites, thiosynergists, sterically hindered amines or UVabsorbers.

Preference is given to using primary antioxidants such as, for example,Irganox 1010 or Irganox 254, alone or in combination with secondaryantioxidants such as, for example, Irgafos TNPP or Irgafos 168.

These ageing inhibitors may be used in any desired combination with oneanother, with mixtures of primary and secondary antioxidants incombination with light stabilizers such as Tinuvin 213, for example,exhibiting particularly good ageing-inhibition effect.

Ageing inhibitors in which a primary antioxidant is united with asecondary antioxidant in one molecule have proved to be especiallyadvantageous. These ageing inhibitors comprise cresol derivatives whosearomatic ring is substituted at two arbitrary, different locations,preferably in ortho- and meta-position relative to the OH group, bythioalkyl chains, it also being possible for the sulphur atom to bejoined to the aromatic ring of the cresol building block via one or morealkyl chains. The number of carbon atoms between the aromatic moiety andthe sulphur atom may be between 1 and 10, preferably between 1 and 4.The number of carbon atoms in the alkyl side chain may be between 1 and25, preferably between 6 and 16. Particularly preferred in this contextare compounds of the 4,6-bis(dodecylthiomethyl)-o-cresol,4,6-bis(undecylthiomethyl)-o-cresol, 4,6-bis(decyl-thiomethyl)-o-cresol4,6-bis(nonylthiomethyl)-o-cresol or 4,6-bis(octylthiomethyl)-o-cresoltype. Ageing inhibitors of these kinds are available for example fromthe company Ciba Geigy under the name Irganox 1726 or Irganox 1520.

The amount of the ageing inhibitor or ageing inhibitor package addedought to be situated within a range between 0.1 and 10% by weight,preferably in a range between 0.2 and 5% by weight, more preferably in arange between 0.5 and 3% by weight, based on the overall solids content.

Preference is given to a presentation form in the form of a dispersionfor particularly simple miscibility with the adhesive dispersion.Alternatively it is also possible for liquid ageing inhibitors to beincorporated directly into the dispersion, in which case the step ofincorporation ought to be followed by a standing time of a number ofhours, to allow the homogeneous distribution of the ageing inhibitor inthe dispersion or its acceptance into the dispersion particles. Afurther alternative is the addition of an organic solution of the ageinginhibitors to the dispersion.

Suitable concentrations lie in the range from 0.1 up to 5 parts byweight, based on the solids.

For improving the processing properties, the adhesive formulation mayfurther be blended with customary process auxiliaries such asrheological additives (thickeners), defoamers, deaerating agents,wetting agents or flow control agents. Suitable concentrations are inthe range from 0.1 up to 5 parts by weight, based on the solids.

Fillers (reinforcing or non-reinforcing) such as silicon dioxides(spherical, acicular, platelet-shaped or irregular like the fumedsilicas), glass in the form of solid or hollow beads, microballoons,calcium carbonates, zinc oxides, titanium dioxides, aluminium oxides oraluminium oxide hydroxides may serve for fine-tuning the processingproperties and also the technical adhesive properties. Suitableconcentrations are in the range from 0.1 up to 20 parts by weight, basedon the solids.

In one preferred embodiment the adhesive formulation of the inventionhas a bond strength to steel in accordance with ASTM D3330 of at least2.5 N/cm (for an adhesive coatweight of about 100 g/m² on a wovenpolyester carrier, in accordance with the examples).

Suitable carriers include in principle all carrier materials, preferablytextile carriers and more preferably woven fabrics, more particularlywoven polyester fabrics.

As carrier material for the adhesive tape it is possible to use allknown textile carriers such as knitted fabrics, scrims, tapes, braids,tufted textiles, felts, woven fabrics (encompassing plain weave, twilland satin weave), knitted fabrics (encompassing warp knits and otherknits) or nonwoven webs, the term “nonwoven web” comprehending at leastsheetlike textile structures in accordance with EN 29092 (1988) and alsostitchbonded webs and similar systems.

It is likewise possible to use woven and knitted spacer fabrics withlamination.

Spacer fabrics of these kinds are disclosed in EP 0 071 212 B1. Spacerfabrics are mat-like layer structures comprising a cover layer of afibre or filament web, an underlayer and individual retaining fibres orbundles of such fibres between these layers, these fibres beingdistributed over the area of the layer structure, being needled throughthe particle layer and joining the cover layer and the underlayer to oneanother. As an additional although not mandatory feature, the retainingfibres in accordance with EP 0 071 212 B1 contain particles of inertminerals, such as sand, gravel or the like, for example.

The retaining fibres needled through the particle layer hold the coverlayer and the underlayer at a distance from one another and are joinedto the cover layer and the underlayer.

Nonwovens contemplated include, in particular, consolidated staple fibrewebs, but also filament webs, meltblown webs and spunbonded webs, whichgenerally require additional consolidation. Possible consolidationmethods known for webs include mechanical, thermal and chemicalconsolidation. Whereas with mechanical consolidations the fibres areheld together purely mechanically usually by entanglement of theindividual fibres, by the interlooping of fibre bundles or by thestitching-in of additional threads, it is possible by thermal and bychemical techniques to obtain adhesive (with binder) or cohesive(binderless) fibre-fibre bonds. Given appropriate formulation and anappropriate process regime, these bonds may be restricted exclusively,or at least predominantly, to fibre nodal points, so that a stable,three-dimensional network is formed while nevertheless retaining therelatively loose, open structure in the web.

Webs which have proved to be particularly advantageous are thoseconsolidated in particular by overstitching with separate threads or byinterlooping.

Consolidated webs of this kind are produced for example on stitchbondingmachines of the “Malimo” type from the company Karl Mayer, formerlyMalimo, and can be obtained from companies including Techtex GmbH. AMalifleece is characterized in that a cross-laid web is consolidated bythe formation of loops from fibres of the web.

The carrier used may also be a web of the Kunit or Multilknit type. AKunit web is characterized in that it originates from the processing ofa longitudinally oriented fibre web to form a sheetlike structure whichhas loops on one side and has loop feet or pile fibre folds on the otherside, but possesses neither threads nor prefabricated sheetlikestructures. A web of this kind as well has been produced for arelatively long time, for example on stitchbonding machines of the“Malimo” type from the company Karl Mayer. A further characterizingfeature of this web is that, as a longitudinal-fibre web, it is able toabsorb high tensile forces in the longitudinal direction. Thecharacteristic feature of a Multiknit web relative to the Kunit web isthat the web is consolidated on both the top and bottom sides by virtueof the double-sided needle punching. The starting product used for aMultiknit is generally one or two single-sidedely interlooped pile fibrenonwovens produced by the Kunit process. In the end product, both topsides of the nonwovens are shaped by means of interlooped fibres to forma closed surface, and are joined to one another by fibres which standalmost perpendicularly. An additional possibility is to introducefurther needlable sheetlike structures and/or scatterable media.

Finally, stitchbonded webs as an intermediate are also suitable forforming a liner of the invention and an adhesive tape of the invention.A stitchbonded web is formed from a nonwoven material having a largenumber of stitches extending parallel to one another. These stitches arebrought about by the stitching-in or stitchbonding of continuous textilethreads. For this type of web, stitchbonding machines of the “Malimo”type from the company Karl Mayer are known.

Also particularly suitable are needlefelt webs. In a needlefelt web, atuft of fibres is made into a sheetlike structure by means of needlesprovided with barbs. By alternate introduction and withdrawal of theneedles, the material is consolidated on a needle bar, with theindividual fibres interlooping to form a firm sheetlike structure. Thenumber and configuration of the needling points (needle shape,penetration depth, double-sided needling) determine the thickness andstrength of the fibre structures, which are in general lightweight,air-permeable and elastic.

Also particularly advantageous is a staple fibre web which ismechanically preconsolidated in the first step or is a wet-laid web laidhydrodynamically, in which between 2% and 50% by weight of the webfibres are fusible fibres, more particularly between 5% and 40% byweight of the web fibres.

A web of this kind is characterized in that the fibres are laid wet or,for example, a staple fibre web is preconsolidated by the formation ofloops from fibres of the web by needling, stitching or air-jet and/orwater-jet treatment.

In a second step, thermofixing takes place, with the strength of the webbeing increased again by the melting, or partial melting, of the fusiblefibres.

For the utilization of nonwovens in accordance with the invention, theadhesive consolidation of mechanically preconsolidated or wet-laid websis of particular interest, it being possible for said consolidation totake place by way of the addition of binder in solid, liquid, foamed orpaste-like form. A great diversity of theoretical presentation forms ispossible: for example, solid binders as powders for trickling in; as asheet or as a mesh; or in the form of binding fibres. Liquid binders maybe applied as solutions in water or organic solvents, or as adispersion. For adhesive consolidation, binding dispersions arepredominantly selected: thermosets in the form of phenolic or melamineresin dispersions, elastomers as dispersions of natural or syntheticrubbers or, usually, dispersions of thermoplastics such as acrylates,vinyl acetates, polyurethanes, styrene-butadiene systems, PVC, and thelike, and also copolymers thereof. Normally the dispersions areanionically or nonionically stabilized, although in certain casescationic dispersions may also be of advantage.

The binder may be applied in a manner which is in accordance with theprior art and for which it is possible to consult, for example, standardworks of coating or of nonwoven technology such as “Vliesstoffe” (GeorgThieme Verlag, Stuttgart, 1982) or “Textiltechnik-Vliesstofferzeugung”(Arbeitgeberkreis Gesamttextil, Eschborn, 1996).

For mechanically preconsolidated webs which already possess sufficientcomposite strength, the single-sided spray application of a binder isappropriate for producing specific changes in the surface properties.

Such a procedure not only is sparing in its use of binder but alsogreatly reduces the energy requirement for drying. Since no squeezerolls are required and the dispersions remain predominantly in the upperregion of the nonwoven, unwanted hardening and stiffening of the web canbe largely prevented.

For sufficient adhesive consolidation of the web carrier, the additionof binder in the order of magnitude of 1% to 50%, more particularly 3%to 20%, based on the weight of the fibre web, is generally required.

The binder may be added as early as during the manufacture of the web,in the course of mechanical preconsolidation, or else in a separateprocess step, which may be carried out in-line or off-line. Followingthe addition of binder, it is necessary temporarily to generate acondition for the binder in which the binder becomes adhesive andadhesively connects the fibres—this may be achieved during the drying,for example, of dispersions, or else by means of heating, with furtherpossibilities for variation existing by way of areal or partialapplication of pressure. The binder may be activated in known dryingtunnels, given an appropriate selection of binder, or else by means ofinfra-red radiation, UV radiation, ultra-sound, high-frequency radiationor the like. For the subsequent end use it is sensible, though notabsolutely necessary, for the binder to have lost its tack following theend of the web production process. It is advantageous that, as a resultof thermal treatment, volatile components such as fibre assistants areremoved, giving a web having favourable fogging values, so that when alow-fogging adhesive is used, it is possible to produce an adhesive tapehaving particularly favourable fogging values; accordingly, the liner aswell has a very low fogging value.

By fogging (see DN 75201 A) is meant the effect where, underunfavourable conditions, compounds of low molecular mass may outgas fromthe adhesive tapes and condense on cold parts. As a result of this it ispossible, for example, for the view through the windscreen to beadversely affected.

A further special form of adhesive consolidation involves activating thebinder by partial dissolution or partial swelling. In this case it isalso possible in principle for the fibres themselves, or admixedspeciality fibres, to take over the function of the binder. Since,however, such solvents are objectionable on environmental grounds,and/or are problematic in their handling, for the majority of polymericfibres, this process is not often employed.

Advantageously and at least in regions, the carrier may have asingle-sidedly or double-sidedly polished surface, preferably in eachcase a surface polished over the whole area. The polished surface may bechintzed, as elucidated in detail in EP 1 448 744 A1, for example.

Furthermore, the carrier may be compacted by calendering on a roll mill.The two rolls preferably run in opposite directions and at the sameperipheral speed, causing the carrier to be pressed and compacted.

If there is a difference in the peripheral speed of the rolls, then thecarrier is additionally polished.

Starting materials for the carrier material for the adhesive tape aremore particularly (manmade) fibres (staple fibre or continuous filament)made from synthetic polymers, also called synthetic fibres, made frompolyester, polyamide, polyimide, aramid, polyolefin, polyacrylonitrileor glass, (manmade) fibres made from natural polymers such as cellulosicfibres (viscose, Modal, Lyocell, Cupro, acetate, triacetate, Cellulon),such as rubber fibres, such as plant protein fibres and/or such asanimal protein fibres and/or natural fibres made of cotton, sisal, flax,silk, hemp, linen, coconut or wool. The present invention, however, isnot confined to the materials stated; it is instead possible, as evidentto the skilled person without having to take an inventive step, to use amultiplicity of further fibres in order to produce the carrier.

Likewise suitable, furthermore, are yarns fabricated from the fibresspecified.

In the case of woven fabrics or scrims, individual threads may beproduced from a blend yarn, and thus may have synthetic and naturalconstituents. Generally speaking, however, the warp threads and the weftthreads are each formed of a single kind.

The warp threads and/or the weft threads here may in each case becomposed only of synthetic threads or only of threads made from naturalraw materials—in other words, of a single kind.

Also suitable for the adhesive tape is a carrier material which consistsof paper, of a laminate, of a film (for example PP, PE, PET, PA, PU), offoam or of a foamed film.

These non-textile sheetlike materials are especially appropriate whenspecific requirements necessitate such a modification of the invention.Films are generally thinner in comparison to textiles, for example, and,as a result of the imperforate layer, offer additional protectionagainst penetration by chemicals and service fluids such as oil, petrol,antifreeze and the like into the actual cable area, and can besubstantially adapted to requirements by an appropriate selection of thematerial from which they are constructed. With polyurethanes orpolyolefin copolymers, for example, flexible and elastic jackets can beproduced; with polyester and polyamides, good abrasion resistance andtemperature stability are achieved.

Foams or foamed films, on the other hand, possess the qualities of moresubstantial space filling and of good soundproofing—where a length ofcable is laid, for example, in a duct-like or tunnel-like area in thevehicle, a jacketing tape of appropriate thickness and soundproofing canprevent disruptive flapping and vibration from the outset.

The adhesive tape may ultimately have a liner material, with which theone or two layers of adhesive are lined before use. Suitable linermaterials also include all of the materials set out comprehensivelyabove.

It is preferred to use a non-linting material such as a polymeric filmor a well-sized, long-fibre paper.

If the adhesive tape described is to be of low flammability, thisquality can be achieved by adding flame retardants to the carrier and/orto the adhesive. These retardants may be organobromine compounds, ifrequired with synergists such as antimony trioxide, although, withregard to the absence of halogen from the adhesive tape, preference willbe given to using red phosphorus, organophosphorus compounds, mineralcompounds or intumescent compounds such as ammonium polyphosphate, aloneor in conjunction with synergists.

The general expression “adhesive tape” in the context of this inventionencompasses all sheetlike structures such as two-dimensionally extendedsheets or sheet sections, tapes with extended length and limited width,tape sections and the like, and also, lastly, diecuts or labels.

The adhesive tape may be produced in the form of a roll, in other wordsrolled up onto itself in the form of an archimedian spiral.

Applied to the reverse of the adhesive tape may be a reverse-facevarnish, in order to exert a favourable influence on the unwindproperties of the adhesive tape wound into the archimedian spiral. Thisreverse-face varnish may for this purpose be furnished with siliconecompounds or fluorosilicone compounds and also withpolyvinylstearylcarbamate, polyethyleneiminestearylcarbamide ororganofluorine compounds as abhesive substances.

The adhesive may be applied in the longitudinal direction of theadhesive tape, in the form of a stripe, the width of the stripe beinglower than that of the carrier of the adhesive tape.

Depending on the particular utility, there may also be a plurality ofparallel stripes of the adhesive coated on the carrier material.

The position of the stripe on the carrier is freely selectable, withpreference being given to an arrangement directly at one of the edges ofthe carrier.

The adhesive is preferably applied over the full area to the carrier.

Provided on the adhesive coating of the carrier there may be at leastone stripe of a covering, extending in the longidutinal direction of theadhesive tape and covering between 20% and 90% of the adhesive coating.

The stripe preferably covers in total between 50% and 80% of theadhesive coating. The degree of coverage is selected according to theapplication and to the diameter of the cable loom.

The percentage figures indicated relate to the width of the stripes ofthe covering in relation to the width of the carrier.

In accordance with one preferred embodiment of the invention there isprecisely one stripe of the covering present on the adhesive coating.

The position of the stripe on the adhesive coating is freely selectable,with preference being given to an arrangement directly at one of thelongitudinal edges of the carrier. In this way an adhesive stripe isproduced which extends in the longitudinal direction of the adhesivetape and finishes at the other longitudinal edge of the carrier.

Where the adhesive tape is used for jacketing a cable harness, by theadhesive tape being passed in a helicoidal movement around the cableharness, the wrapping of the cable harness may be accomplished bybonding the adhesive of the adhesive tape only to the adhesive tapeitself, with the substrate not coming into contact with any adhesive.

The cable harness jacketed in this way has a very high flexibility, as aresult of the absence of fixing of the cable by any adhesive.Consequently the flexibility of said cable harness oninstallation—particularly in narrow passages or sharp bends—issignificantly increased.

If a certain degree of fixing of the adhesive tape on the substrate isdesired, the jacketing may be accomplished by bonding part of theadhesive stripe to the adhesive tape itself and another part to thesubstrate.

In accordance with another advantageous embodiment, the stripe isapplied centrally on the adhesive coating, thereby producing twoadhesive stripes extending on the longitudinal edges of the carrier inthe longitudinal direction of the adhesive tape.

For the secure and economic application of the adhesive tape in saidhelicoidal movement around the cable harness, and to counter theslipping of the resultant protective wrapping, the two adhesive stripeseach present on the longitudinal edges of the adhesive tape areadvantageous, especially if one stripe, which is usually narrower thanthe second stripe, serves as a fixing aid and the second, broader stripeserves as a fastener. In this way, the adhesive tape is bonded to thecable in such a way that the cable harness is secured against slippingbut is nevertheless of flexible design.

In addition there are embodiments in which more than one stripe of thecovering is applied to the adhesive coating. Where reference is madeonly to one stripe, the skilled person reads this, conceptually, asaccommodating the possibility that there may well be two or more stripescovering the adhesive coating at the same time.

The procedure for producing the adhesive tape of the invention involvesnothing more than the coating of the carrier directly with thedispersion in one or more operations carried out in succession. In thecase of textile carriers, the untreated textile can be coated directlyor by a transfer process. Alternatively the textile may be pretreatedwith a coating (using any desired film-forming substance from solution,dispersion, melt and/or radiation-curing), before then being provided,in a downstream work-step, directly or by a transfer process, with thePSA.

Application assemblies used are the customary ones: wire doctor, coatingbar, roll application, nozzle coating, twin-chamber doctor blade,multiple cascade die.

On the basis of the positive properties outlined, the adhesive tape canbe used outstandingly for insulating and wrapping wires or cables.

Furthermore, it is advantageously suitable for the jacketing of elongatematerial such as, more particularly, cable looms in motor vehicles, withthe adhesive tape being passed in a helical line around the elongatematerial, or the elongate material being wrapped in axial direction bythe tape.

Lastly, the concept of the invention also embraces an elongate materialjacketed with an adhesive tape of the invention. The elongate materialis preferably a cable loom.

On account of the outstanding suitability of the adhesive tape, it canbe used in a jacket that consists of a covering, where, at least in oneedge region of the covering, the self-adhesive tape is present, and isbonded on the covering in such a way that the adhesive tape extends overone of the longitudinal edges of the covering, and preferably in an edgeregion which is narrow by comparison with the width of the covering.

One such product and also optimized embodiments thereof are disclosed inEP 1 312 097 A1. EP 1 300 452 A2, DE 102 29 527 A1 and WO 2006 108 871A1 show ongoing developments for which the adhesive tape of theinvention is likewise very suitable. The adhesive tape of the inventionmay also find use in a method of the kind disclosed by EP 1 367 608 A2.

Finally, EP 1 315 781 A1 and DE 103 29 994 A1 describe embodiments ofadhesive tapes of a kind also possible for the adhesive tape of theinvention.

With further preference the adhesive tape, in bonding to cables with PVCjacketing and to cables with polyolefin jacketing, does not destroythese systems when an assembly composed of cables and adhesive tape is,in accordance with LV 312, stored at temperatures above 100° C. for upto 3000 hours and then the cables are bent around a mandrel.

The adhesive tape of the invention is outstandingly suitable for thewrapping of cables, can be easily unwound for simple processing,exhibits little or no flagging, and exhibits no cable embrittlement evenin the high temperature classes T3 and T4 over 3000 hours.

The purpose of the text below is to illustrate the adhesive tape using anumber of figures, without wishing thereby to bring about a restrictionof whatever kind.

FIG. 1 shows one embodiment of an adhesive tape according to theinvention in a lateral section,

FIG. 2 shows a cut-out section of a cable harness which is composed of abundle of individual cables and is jacketed with the adhesive tape ofthe invention,

FIG. 3 shows an advantageous application of the adhesive tape,

FIG. 4 shows a test specimen in schematic,

FIG. 5 shows a test specimen with the assembly perforated,

FIG. 6 shows a test specimen bonded centrally to strips of a broaderadhesion base so that the small piece of card still overlaps just at theend, and

FIG. 7 shows the finished test samples, in other words the test stripstogether with adhesion base adhered to the card core in such a way thatthe upper end of the test specimen overaps the vertex point by a smallamount.

Shown in FIG. 1, in a section in the transverse direction (transversesection), is the adhesive tape, consisting of a woven fabric carrier 1,on one side of which a layer of a self-adhesive coating 2 is applied.

FIG. 2 shows a cut-out section of a cable harness which is composed of abundle of individual cables 7 and is jacketed with the adhesive tape 11of the invention. The adhesive tape is passed in a helicoidal movementaround the cable harness.

The cut-out section of cable harness shown has two turns I and II of theadhesive tape. Further turns would extend towards the left, but are notshown here.

In a further embodiment for jacketing, two tapes 60, 70 of theinvention, furnished with an adhesive, are laminated with theiradhesives at an offset (preferably by 50% in each case) to one another,producing a product as shown in FIG. 3.

EXAMPLES Outline of the Examples

The adhesive tape of the invention is described below in a preferredembodiment by means of a number of examples, without wishing thereby tosubject the invention to any restriction whatsoever.

In addition, comparative examples are given, which show unsuitableadhesive tapes.

To illustrate the invention, example adhesive tapes were producedaccording to the following scheme:

The PSA dispersions were mixed from polymer dispersion and resindispersion in line with the example formulas, and were intimatelyhomogenized using a stirrer. The PSA dispersions were subsequentlyadjusted, by stirred incorporation of a polyurethane associativethickener (Borchigel 0625, OMG Borchers), to a viscosity ofapproximately 5000 Pa*s at a shear rate of 0.01 s⁻¹ (measured usingcone/plate geometry in rotation mode with a DSR 200 N rheometer fromRheometric Scientific).

Using a film-drawing apparatus, a woven polyester fabric (linear fibredensity 167 dtex, thread count warp 48.5 1/cm, thread count weft 231/cm) was coated with the thickened example PSA dispersion in such a wayas to result, after drying in a forced-air oven at 85° C. for 5 minutes,in an adhesive coatweight of approximately 20 g/m².

In a second work-step, the fabric impregnated in this way was coatedanalogously with the same dispersion, so as to result, after drying in aforced-air oven at 85° C. for 10 minutes, in a total adhesive coatweightof 100 g/m².

Assessment Criteria

The criteria for an application-compatible adhesive tape for thewrapping of cables are

-   -   unwind force from rolls after storage at 40° C. for 4 weeks    -   flagging resistance as per the TFT test    -   cable compatibility according to LV 312

Procedure of the Tests

Unless expressly stated otherwise, the measurements are carried outunder test conditions of 23±1° C. and 50±5% relative humidity.

Measurement of Unwind Force to LV312

Here, a value in the range from about 3 to 9 N/cm at a take-off speed of30 m/min is considered to be compatible with the application and isscored as “1”. Values outside the range receive a score of “0”.

Measurement of Flagging Resistance to LV312 or TFT Method (ThresholdFlagging Time)

For determining the flagging behaviour by the TFT method, a test isemployed in which an additional flexural stress is generated by theapplication of the test specimens, prepared in a flat format, to a 1½″core. The combination of tensile load by a test weight and flexuralstress causes flagging-like detachment of the adhesive tape startingfrom the bonded upper end, and ultimate failure by dropping of the testspecimens (see FIG. 4, which also shows the schematic construction).

The time in minutes before dropping is the result.

The critical parameters for the holding time of the test specimens areweight and temperature, the weight being selected such as to result invalues of at least 100 minutes.

The cylindrically shaped test mandrel is a 1½″ card core with anexternal diameter of 42±2 mm, provided with a marking line 5 mm adjacentto the vertex line.

The adhesion base is the adhesive tape's own reverse face.

The manual roller has a weight of 2 kg.

The test weight is 1 kg.

The test conditions are 23±1° C. and 50±5% relative humidity, or 40° C.in the heating cabinet.

The test is carried out on strips of adhesive tape 19 mm wide. A stripwith a length of 400 mm is adhered to release paper and cut to formthree strips with a length of 100 mm each. This should be done using afresh cutter blade. The reverse face must not be touched.

A small piece of card is adhered beneath one of the ends of each strip,and the assembly is perforated (see FIG. 5).

The test strips are then individually bonded centrally to strips of thebroader adhesion base (adhesive tape with a width 1½ times that of theadhesive tape under test), so that the small piece of card stilloverlaps just (2 to 3 mm) at the end (see FIG. 6).

The test specimens are rolled down using the 2 kg manual roller at arate of 10 m/min in 3 cycles.

The finished test samples, in other words the test strips together withadhesion base, are then adhered to the card core in such a way that theupper end of the test specimen overaps the vertex point by 5 mm (seeFIG. 7). In this operation, only the adhesion base, and not the testspecimen, must be pressed on.

The test specimens fully prepared are left for 20±4 hours without weightloading in a controlled-climate chamber at 40° C.

Weights with a mass of one kilogram are then hung onto the specimens,and the stopwatches are started.

The measurement ends after failure of all three test specimens of onesample.

The median of the three individual measurements is reported in minutes.

The holding time is reported in minutes.

In this context, a TFT value of >1200 minutes is considered to be alower limit with regard to resistance to flagging.

Values below this receive a score of 0, values from 1201 to 2000 minutesreceive a score of 1, values from 2001 to 5000 minutes receive a scoreof 2, and values above 5001 minutes receive a score of 3. Thesegradations reflect increasing security against flagging.

Measurement of Cable Compatibility to LV312

Cable compatibility is considered to exist when there is noembrittlement after 3000 hours at 150° C. on bending around a mandrelwith a diameter of 2 mm, and this is given a score of “1”. Valuesoutside this receive a score of “0”.

Measurement of Bond Strength

For measuring the bond strength of the pure dispersions, coated-outsamples of the adhesives were prepared first of all. For this purpose,the dispersions were applied to a PET film (polyethylene terephthalate)with a thickness of 23 μm, and were drawn down using a film-drawingapparatus in such a way as to result, after drying for 5 minutes at 105°C. in a forced-air drying cabinet, in an adhesive coatweight of 30 g/m².

Using a cutter knife, strips 20 mm wide and 25 cm long were cut fromthis sheet.

For measuring the bond strength of the formulations with resin,coated-out samples were drawn down as described above onto wovenpolyester fabrics, and likewise cut using a cutter knife into strips 20mm wide and 25 cm long.

The bond strength to steel was measured in accordance with ASTM D3330.

Measurement of Glass Transition Temperatues

The glass transition temperatures were determined on the DSC 204 F1“Phönix” Dynamic Differential Scanning Calorimeter from Netzsch,Germany, in 25 μl aluminium crucibles with a perforated lid, under anitrogen atomosphere (20 ml/min gas flow rate). The initial sample masswas 8±1 mg. The samples were subjected to measurement twice from −140°C. to 200° C., with a heating rate of 10 K/min. The subject analysis wasthe 2nd heating curve.

The method is based on DIN 53 765.

Composition of Example Polymer Dispersions

To illustrate the concept of the invention, polymer dispersions havingthe following comonomer composition were trialled:

Monomer Polymer 1 Polymer 2 Polymer 3 2-Ethylhexyl acrylate 93  92 Butyl acrylate 95  Acrylic acid 4 2 1 Acrylonitrile 3 — — Methylmethacrylate — 6 — Vinyl acetate — — 4

The bond strengths to steel of polymers 1 to 3 were measured as follows(figure in N/cm):

Polymer 1 Polymer 2 Polymer 3 2.8 1.4 1.9

The glass transition temperatures of polymers 1 to 3 were measured asfollows (figure in ° C.):

Polymer 1 Polymer 2 Polymer 3 −47 −48 −36

Polymer 1 was used to formulate the pressure-sensitive adhesives (PSAs)listed in Table 1, by blending with dispersions of tackifier resin. Thenumber here indicates the parts by weight of tackifier relative to 100parts by weight of polymer 1 (based in each case on solids).

TABLE 1 Adhesive formulations from polymer 1 Softening InventiveComparative point examples examples Tackifier type ° C. B1 B2 B3 V1 V2V3 Rosin ester resin 99 45 10 Snowtack 100G, Lawter Rosin ester resin 8340 Snowtack 780 G, Lawter Rosin acid resin 69 40 Snowtack 781A*, LawterTerpene phenolic resin 96 35 Dermulsene TR 602, DRT *Former designation:Snowtack SE 380.

Serving as Inventive examples B4 and B5 are polymers 2 and 3, in eachcase blended with 40 parts by weight of the rosin ester resin Snowtack100G with a softening point of 99° C.

Counter-example V4 is the acrylate dispersion Primal PS 83 D from themanufacturer Dow Chemical Company, blended with 8 parts by weight ofSnowtack 781A, with the former designation Snowtack SE 380. This examplerelates to Inventive example 1 of DE 44 19 169 A1.

The bond strengths to steel of Inventive examples B1 to B5 and also ofCounter-examples V1 to V4 were measured as follows (figure in N/cm):

B1 B2 B3 B4 B5 V1 V2 V3 V4 4.6 4.3 3.9 3.8 3.4 2.2 1.9 1.8 2.1

The glass transition temperatures of the pressure-sensitive adhesiveformulations of Inventive examples B1 to B5 and also of Counter-examplesV1 to V4 were measured as follows (figure in ° C.):

B1 B2 B3 B4 B5 V1 V2 V3 V4 −26 −29 −33 −25 −16 −32 −39 −47 −37

Table 3 sets out the test results for the example specimens:

TABLE 3 Inventive Comparative examples examples B1 B2 B3 B4 B5 V1 V2 V3V4 Unwind force 1 1 1 1 1 1 1 1 1 Flagging 3 2 3 1 2 0 0 0 0 resistanceCable 1 1 1 1 1 1 1 1 1 compatibility

All three test criteria are vital for an application-compatible adhesivetape for cable jacketing. The inventive examples therefore show adhesivetapes which conform to the concept of the invention; the comparativeexamples, in contrast, are unsuitable.

1. Adhesive tape consisting of a textile carrier and of apressure-sensitive adhesive which is applied on at least one side of thecarrier and is in the form of a dried polymer dispersion, the polymerbeing synthesized from: a) 90% to 99% by weight of n-butyl acrylateand/or 2-ethylhexyl acrylate, b) 0% to 10% by weight of an ethylenicallyunsaturated monomer having an acid or acid-anhydride function, c) 10% to1% by weight of one or more ethylenically unsaturated monofunctionalmonomers different from (a) and (b), and d) 0% to 1% by weight of adifunctional or polyfunctional monomer, and the pressure-sensitiveadhesive comprising between 15 and 100 parts by weight of a tackifier(based on the mass of the dried polymer dispersion).
 2. Adhesive tapeaccording to claim 1, wherein acrylonitrile and/or methacrylonitrileform the monomer (c) or at least part of the monomers (c).
 3. Adhesivetape according to claim 1, wherein 2-ethylhexyl acrylate forms monomer(a).
 4. Adhesive tape according to claim 1, wherein the monomer (a)consists of 2-ethylhexyl acrylate and at the same time the monomer (c)or at least part of the monomers (c) consists of acrylonitrile and/ormethacrylonitrile.
 5. Adhesive tape according to claim 1, wherein themonomer (b) is acrylic acid, methacrylic acid, itaconic acid, maleicacid, fumaric acid and/or maleic anhydride.
 6. Adhesive tape accordingto claim 1, wherein monomer (d) is divinylbenzene, an alkyl diacrylate,a triacrylate or a tetraacrylate.
 7. Adhesive tape according to claim 1,wherein 20 to 80 parts by weight of tackifiers have been added. 8.Adhesive tape according to claim 1, wherein tackifiers used aretackifier resins having a softening point of more than 80° C. inaccordance with ASTM E28-99 (2009).
 9. Adhesive tape according to claim1, wherein the glass transition temperature of the pressure-sensitiveadhesive is less than +15° C. (determined by DSC (Differential ScanningCalorimetry) in accordance with DIN 53 765 with a heating rate of 10K/min).
 10. Adhesive tape according to claim 1, wherein thepressure-sensitive adhesive according to ASTM D3330 has a bond strengthto steel of at least 2.5 N/cm (for an adhesive coatweight of 100 g/m² ona woven polyester fabric carrier).
 11. Adhesive tape according to claim1, wherein the carrier is a textile carrier.
 12. Method of using anadhesive tape according to claim 1 for jacketing elongate material,comprising passing the adhesive tape in a helical line around theelongate material.
 13. Method of using an adhesive tape according toclaim 1 for jacketing elongate material, comprising wrapping theelongate material in axial direction by the tape.
 14. Elongate materialjacketed with an adhesive tape according to claim
 1. 15. Elongatematerial according to claim 14, which is a cable loom.